Method for producing a retort for a nitriding furnace and retort

Abstract

A method for producing a retort for a nitriding furnace, in which metallic workpieces are heat-treated in a pre-determined atmosphere, includes pickling at least the surfaces of the retort, which are configured to come into contact with the pre-determined atmosphere while the nitriding furnace is operating, by using a pickling agent. The pickled surfaces may then be electropolished and passivated. A retort may be produced according to this method and the retort may be used in a nitriding furnace.

The invention claimed is: 
     
       1. A method for producing a retort for a nitriding furnace, in which metallic workpieces are heat-treated in a pre-determined atmosphere, wherein the retort is produced from a stainless steel, comprising:
 pickling at least the surfaces of the retort, which are configured to come into contact with the pre-determined atmosphere while the nitriding furnace is operating, by using a pickling agent; and 
 after pickling, polishing the surfaces by using an electrolyte in a galvanic bath. 
 
     
     
       2. The method according to  claim 1 , wherein the pickling agent comprises nitric acid and hydrofluoric acid. 
     
     
       3. The method according to  claim 1 , wherein the electrolyte comprises phosphoric acid and sulfuric acid. 
     
     
       4. The method according to  claim 1 , further comprising passivating the polished surfaces with nitric acid. 
     
     
       5. The method according to  claim 1 , wherein the retort is cylindrical shaped, and the retort is made from metal sheet cut-outs, which are welded together. 
     
     
       6. The method according to  claim 1 , wherein the retort is made from metal sheet cut-outs, which are welded together. 
     
     
       7. The method according to  claim 1 , wherein the retort is cylindrical shaped. 
     
     
       8. The method according to  claim 1 , wherein the retort concentrically encompasses a guide cylinder configured to hold the metallic workpieces during operation. 
     
     
       9. The retort method according to  claim 8 , wherein:
 the retort is made from metal sheet cut-outs, which are welded together; and 
 the retort is cylindrical shaped. 
 
     
     
       10. The method according to  claim 4 , wherein the pickling agent comprises nitric acid and hydrofluoric acid. 
     
     
       11. The method according to  claim 10 , wherein the electrolyte comprises phosphoric acid and sulfuric acid. 
     
     
       12. The method according to  claim 11 , wherein the retort is cylindrical shaped and the retort is made from metal sheet cut-outs, which are welded together. 
     
     
       13. The method according to  claim 12 , wherein inner surfaces of the retort are pickled, electropolished and passivated. 
     
     
       14. The method according to  claim 12 , wherein the pre-determined atmosphere contains ammonia. 
     
     
       15. The method according to  claim 1 , wherein the pre-determined atmosphere contains ammonia.